The present invention relates to a platen and platen cover of a photocopying machine and, more particularly to an intermediate transparent cover to prevent displacement of an original document on the platen.
A typical photographic copying machine is provided with a transparent platen which supports an original document during a copying process. The transparent platen allows graphic information on the original document to be scanned by an optical system within the copying machine. A scanning system then projects an image of the graphic information to a photoconductive member thereby creating a latent electrostatic image of the graphic information on the photoconductive member. The latent electrostatic image is developed on the photoconductive member by the application of colored marking material, which is transferred to another support material, usually plain paper, to form a photocopy of the graphic information on the original document.
The original document is illuminated by a source of high intensity light for photocopying. Typical techniques for illuminating the original document are scanning, which involves a relative movement between the original document and the source of illumination, or by a full-frame high Intensity flash exposure of the original document while both the original document and the light source remain stationary, even though the photoconductive member may be moving at the instant of the flash of illumination.
An original document is placed face down on the transparent platen to be copied or scanned by illumination from within the copy machine. A platen cover is pivotably mounted by a suitable hinge system adjacent to the platen to be swung down to a position covering the platen and to be swung up to an open position for placement of the original document on the platen or removal of the original document from the platen.
The platen cover holds and secures the original document on the platen. The platen cover typically has a white lower surface to provide a white background for a photocopy of an original document that does not fill the platen area to prevent black framing in copies of less than full-size originals.
When the original document is positioned on the platen and the platen cover is being lowered to close, air currents caused by the closing of the platen cover frequently cause the original document to be displaced, often resulting in off-center copying. This problem is exacerbated with small or light-weight documents or with multiple documents that have to be precisely positioned relative to each other on the platen.
The heavy electric current used in a present day copying machine and the resulting electric fields coupled with the extensive use of glass and plastics in the platen and platen cover creates electrostatic charges on the platen or the platen cover or both. These electrostatic charges also cause the original document on the platen to be displaced during closing of the platen cover.
It is an object of this invention to provide a platen cover to prevent displacement of an original document.
According to the present invention, an intermediate platen cover is provided between a platen and a platen cover of a photocopying machine to prevent displacement of a document on the platen. The intermediate platen cover is transparent to allow the user to see placement of the document and to not interfere with the background lower surface of the platen cover during photocopying. The intermediate platen cover can be hinged with the platen cover or attached along any of the sides around the platen. The intermediate platen cover can be tethered to the photocopying machine or freestanding. The upper surface of the intermediate platen cover can be repositionably adhesive to help attach and position the document to the intermediate platen cover before lowering into position on the platen.
Other objects and attainments together with a fuller understanding of the invention will become apparent and appreciated by referring to the following description and claims taken in conjunction with the accompanying drawings.